When you smell an offensive sewer smell coming from your kitchen sink drain, the smell indicates a problem with the sink or house plumbing. Troubleshoot possible causes of the smell immediately, as the presence of sewer gasses in your home can be toxic if you inhale them long enough.
Every drain pipe in your house connects to a vent pipe, which serves a dual purpose. The vent pipes replace any air lost down the drain with waste water, keeping the same amount of air in the drains so water levels stay the same. The vent pipe also gives an escape route for the sewer gasses that have made their way into the drain pipes, instead of the sewer gasses pushing their way through the drains and into the house. To see if your vent pipe is clogged, climb onto the roof and shine a flashlight down it. Shoot water down the pipe with a garden hose to dislodge clogs so the pipe functions as it should.
Every plumbing fixture in your house has a trap in its drain pipe. You will see the trap, or the curving section of pipe, located under your kitchen sink. The trap curves so it always stays full of water as long as the plumbing is functioning normally. The water in the trap will block any sewer gasses from coming through the pipe. Leaking pipe connections or evaporation will drain the trap enough that sewer gasses will come through into the sink's drain opening.
Every sink drain in your house, including in your kitchen, may develop a slime of biological materials such as soap, skin oils and even hair. The slime clings to the sides of the drain pipe, near the drain opening. Bacteria will grow readily in the slime, which produces an offensive odour similar to a sewer. Once the slime takes hold, you must wash it off the drain pipe's walls using a bottle brush and hot, soapy water.
Always run your garbage disposal for several seconds longer than you think necessary to chop up and dispose of any food debris you have sent down the disposal side of your kitchen sink. Turning off the disposal early will result in food debris and water slamming into the sides of the disposal chamber, according to master plumber Tim Carter, forming a slurry on the sides of the disposal. The slurry will harden and produce a foul odour you will smell in the sink's drain.